Graphene-based modification on the interface in fibre reinforced cementitious composites for improving both strength and toughness

The attainment of both high strength and high toughness is an essential requirement for most structural materials. However, these properties are generally mutually exclusive. To address the conflict between strength and toughness in polyvinyl alcohol (PVA) fibre reinforced cement composites (FRCCs), in this study, we introduced relatively weak interfaces in FRCCs while enhancing the cement matrix in vicinity of the fibre by coating oxidized graphene nanosheets (OGNs) on PVA fibre surfaces. Weak interfaces were introduced due to the sliding between OGNs, while cement matrix in the vicinity of fibre was densified by the strong interaction of OGNs with cement. As a result, this OGNs coating simultaneously improved tensile strength and toughness by 32.0% and 10.0% in the PVA FRCCs. Further investigation also indicated that the oxidation level of the coated OGNs had a significant influence on their interaction with cement. Reduction of OGNs, using L-ascorbic acid for 1 min and 60 min, resulted in 18.6% and 21.7% decrease in interfacial shear strength between fibre and cement, respectively. These reductions also correspondingly caused 114.9% and 117.3% increase in porosity and 36.5% and 35.0% decrease in the stiffness of the cement matrix in the vicinity of fibre.